Thin film photovoltaic module manufacturing methods and structures

Abstract

The present invention provides module structures and methods of manufacturing rigid or flexible photovoltaic modules employing thin film solar cells fabricated on flexible substrates, preferably on flexible metallic foil substrates. The solar cells may be Group IBIIIAVIA compound solar cells or amorphous silicon solar cells fabricated on thin stainless steel or aluminum alloy foils. In one embodiment, initially a solar cell string including two or more solar cells is formed by interconnecting the solar cells with conductive leads or ribbons. At least one bypass diode electrically connects conductive back surfaces of at least two solar cells. The bypass diode and the solar cells are encapsulated with support material and are packed with the protective shell such that the at least one bypass diode is placed between at least one solar cell and the bottom protective sheet. The bypass diode is thermally connected to the back conductive surface of one of the solar cells so that the back conductive surface of the solar cell functions as a heat sink.

1 . A solar module, comprising:
 a solar cell string including a plurality of solar cells including a first solar cell and a second solar cell, each solar cell having a light receiving side and a back side, wherein the back side comprises a conductive substrate and wherein the plurality of solar cells are electrically interconnected in series using conductive leads which connect the light receiving side of one solar cell to the back side of an adjacent solar cell;   a bypass diode device attached to the solar cell string, the bypass diode device including a bypass diode having a first and second leads, and first and second conductive strips each electrically connected at one end to one of the first and second leads respectively and each electrically connected at another end to a first conductive substrate of the first solar cell and a second conductive substrate of the second solar cell, respectively;   an encapsulant having a frontside and a backside that encapsulates the solar cell string and the bypass diode device; and   a protective shell sealing the encapsulated string, the protective shell including a transparent front protective layer, a back protective layer and a moisture barrier seal extending between and sealing edges of the transparent front protective layer and the back protective layer, wherein the transparent front protective sheet is placed over the light receiving side of the plurality solar cells and the frontside of the encapsulant and the back protective sheet is placed under the first and second conductive substrates, the by pass diode device and the backside of the encapsulant such that the bypass diode is located between the back protective sheet and the conductive substrates of the plurality of solar cells.   
     
     
         2 . The solar module of  claim 1 , wherein a thermal connection is established between the bypass diode device and one of the conductive substrates of the plurality of solar cells. 
     
     
         3 . The solar module of  claim 2 , wherein the thermal connection is established by attaching the bypass diode device to one of the conductive substrates using one of a thermally conductive paste and thermally conductive adhesive. 
     
     
         4 . The solar module of  claim 3  wherein the of one the thermally conductive paste and thermally conductive adhesive directly attaches the bypass diode to one of the conductive substrates of the plurality of solar cells 
     
     
         5 . The solar module of  claim 2 , wherein the thermal connection is established by directly mounting the bypass diode to one of the conductive substrates. 
     
     
         7 . The solar module of  claim 1 , wherein the light receiving side of each solar cell includes one of a Group IBIIIAVIA thin film or a amorphous silicon thin film. 
     
     
         8 . The solar module of  claim 1 , wherein the conductive substrate of each solar cell includes one of a stainless steel foil and aluminum foil. 
     
     
         9 . The solar module of  claim 1 , wherein the encapsulant comprises at least one of ethylene vinyl acetate (EVA) and thermoplastic polyurethane (TPU). 
     
     
         10 . The solar module of  claim 1 , wherein the transparent front protective layer comprises one of glass and ETFE (ethylene tetrafluoroethylene), and wherein the back protective layer comprises one of glass and PVF (polyvinyl fluoride). 
     
     
         11 . A method of manufacturing a solar module, comprising:
 providing a front protective layer having a front surface and a back surface, wherein the front protective layer is transparent;   placing a first encapsulant layer over the back surface of the front protective layer;   placing a solar cell string over the first encapsulant layer, wherein the solar cell string includes a plurality of solar cells, each solar cell having a light receiving side and a back side, wherein the back side comprises a conductive substrate and wherein the plurality of solar cells are electrically interconnected in series using conductive leads which connect the light receiving side of one solar cell to the back side of an adjacent solar cell, and wherein the light receiving side of the solar cells face the first encapsulant layer;   attaching a bypass diode device to the solar cell string, the bypass diode device including a first conductive strip and a second conductive strip each attached at one end to respective first and second leads of a bypass diode, wherein the bypass diode is electrically connected to a first conductive substrate of a first solar cell and a second conductive substrate of a second solar cell of the plurality of solar cells by the first conductive strip and the second conductive strip, respectively;   placing a second encapsulant layer over the bypass diode device and the conductive substrates of the plurality of solar cells;   placing a back protective sheet over the second encapsulant layer and sealing a peripheral gap between the periphery of the front protective sheet and the back protective sheet with a moisture barrier edge sealant, and thereby forming a pre-module structure; and   subjecting the pre-module structure to heat and pressure to form the solar module.   
     
     
         12 . The method of  claim 11 , wherein the step of attaching the bypass diode device includes thermally connecting the bypass diode device to one of the conductive substrates of the plurality of solar cells. 
     
     
         13 . The method of  claim 12 , wherein the thermal connection is established by attaching the bypass diode device to one of the conductive substrates using one of a thermally conductive paste and thermally conductive adhesive. 
     
     
         14 . The solar module of  claim 13  wherein the of one the thermally conductive paste and thermally conductive adhesive directly attaches the bypass diode to one of the conductive substrates of the plurality of solar cells 
     
     
         15 . The method of  claim 12 , wherein the thermal connection is established by directly mounting the bypass diode to one of the conductive substrates. 
     
     
         16 . The method of  claim 11  further comprising the step of attaching a junction box to the back protective sheet after forming the solar module. 
     
     
         17 . The method of  claim 11 , wherein the step of subjecting the pre-module structure to heat and pressure is performed in a roll-to-roll laminator. 
     
     
         18 . The method of  claim 11 , wherein the light receiving side of each solar cell includes one of a Group IBIIIAVIA thin film or a amorphous silicon thin film. 
     
     
         19 . The method of  claim 11 , wherein the conductive substrate of each solar cell includes one of a stainless steel foil and aluminum foil. 
     
     
         20 . The method of  claim 11 , wherein the encapsulant layer comprises at least one of ethylene vinyl acetate (EVA) and thermoplastic polyurethane (TPU). 
     
     
         21 . The method of  claim 1 , wherein the front protective layer comprises one of glass and ETFE (ethylene tetrafluoroethylene), and wherein the back protective layer comprises one of glass and PVF (polyvinyl fluoride).